Halftone imaging silver halide emulsions, photographic elements, and processes which employ novel arylhydrazides

ABSTRACT

An unballasted arylhydrazide is disclosed the aryl moiety of which is substituted with a group of the formula ##STR1## where one of X and X&#39; represents -NH-, the other represents a divalent chalcogen, and R represents an aliphatic or aromatic residue. The arylhydrazides, when applied to halftone imaging in conjunction with silver halide emulsions, photographic elements, and imaging processes, produce images of improved dot quality and low levels of pepper fog.

This is a division of application Ser. No. 658,921, filed Oct. 9, 1984(now U.S. Pat. No. 4,560,638).

FIELD OF THE INVENTION

The invention is directed to novel unballasted arylhydazides, to silverhalide emulsions and photographic elements capable of producing halftoneimages, and to processes for their use.

BACKGROUND OF THE INVENTION

Lithographic printing plates contain areas that accept ink, areas thatrepel ink, and, ideally, no areas of intermediate properties. Theillusion that some areas of a printed image are of intermediate densityis created by the viewer's inability to resolve tiny dots of maximumdensity and background areas of minimum density that separate them. Suchimages are referred to as halftone images.

Halftone images are typically produced on lithographic printing platesby contact exposure through a high contrast photographictransparency--often referred to as a lith type photographic element. Tobe useful for the exposure of lithographic printing plates thephotographic element must have a contrast of at least 10 (hereinafterdesignated by reference to high contrast) and more typically near orabove 20. Over and above contrast requirements, however, it is importantthat a lith type photographic element applied to halftone imagingexhibit the characteristic of producing high dot quality. That is, thedots must be well resolved--e.g., with sharp as opposed to soft orragged edges.

The use of hydrazines in negative working surface latent image formingsilver halide emulsions and photographic elements to increase speed andcontrast is taught by Trivelli et al U.S. Pat. No. 2,419,975. Increasedcontrast attributable to hydrazines in negative working surface latentimage forming silver halide emulsions is believed to result from thepromotion of infectious development.

The hydrazines preferred for their higher effectiveness in increasingcontrast are arylhydrazides. The acyl moiety o arylhydrazides increasesactivity while the aryl moiety acts to increase stability. The followingare illustrative of specific arylhydrazides employed with negativeworking surface latent image forming silver halide emulsions primarilyto increase contrast:

P-1: Takada et al.; U.S. Pat. No. 4,168,977

P-2: Takada et al.; U.S. Pat. No. 4,224,401

P-3: Okutsu et al.; U.S. Pat. No. 4,221,857

P-4: Mifune et al.; U.S. Pat. No. 4,243,739

P-5: Mifune et al.; U.S. Pat. No. 4,272,614

P-6: Mifune et al.; U.S. Pat. No. 4,323,645.

While the arylhydrazide is preferably incorporated directly in aphotographic element, it can be incorporated in processing solution forthe element. A preferred processing solution is disclosed in thefollowing patent:

P-7: Nothnagle; U.S. Pat. No. 4,269,929.

In surface latent image forming silver halide emulsions the grains whichare exposed to light are rendered developable while grains which are notexposed to light are not intended to be developed. Nevertheless, some ofthese unexposed grains develop spontaneously. In fulltone imaging thespontaneously developing grains raise minimum density more or lessuniformly. Such minimum density levels are referred to as fog and, solong as they remain low, are not objectionable.

Pepper fog differs from ordinary fog in that it takes the form of small,maximum density areas randomly distributed on a substantially uniformminimum density background. When a photographic element exhibitingpepper fog is viewed under magnification, the impression to the vieweris often that the magnified field of view has been sprinkled with grainsof pepper. It has been long recognized that arylhydrazides producepepper fog, and, until very recently, this has interfered with thecommercial use of arylhydrazides in halftone imaging. An illustration ofsevere pepper fog appears in FIG. 1. FIG. 2 is an illustration of pepperfog at its highest acceptable level. Each of FIGS. 1 and 2 is an actualphotograph of a field of view enlarged 20X.

In addition to their use to increase contrast in negative working silverhalide emulsions arylhydrazides have been employed extensively asnucleating agents in direct positive silver halide emulsions. Whenemployed as a nucleating agent the function of the arylhydrazide is toreplace uniform light exposure or aerial oxidation as a technique forselectively accelerating development of unexposed internal latent imageforming silver halide grains. This increases maximum density withoutincreasing minimum density of the direct positive image. The use of ahydrazine as a nucleating agent was first taught by

P-8: Ives; U.S. Pat. No. 2,563,785.

Exemplary arylhydrazides employed as nucleating agents in internallatent image forming direct positive emulsions are illustrated by thefollowing:

P-9: Whitmore; U.S. Pat. No. 3,227,552

P-10: Leone et al.; U.S. Pat. No. 4,030,925

P-11: Leone et al.; U.S. Pat. No. 4,031,127

P-12: Leone et al.; U.S. Pat. No. 4,080,207

P-13: Tsujino et al.; U.S. Pat. No. 4,245,037

P-14: Hirano et al.; U.S. Pat. No. 4,255,511

P-15: Adachi et al.; U.S. Pat. No. 4,266,013

P-16: Leone; U.S. Pat. No. 4,276,364

RD-1: Research Disclosure, Vol. 151, November 1976, Item 15162

RD-2: Sidhu et al Research Disclosure, Vol. 176, December 1978, Item17626

Research Disclosure is published by Kenneth Mason Publications, Ltd.,The Old Harbourmaster's, 8 North Street, Emsworth, Hampshire P010 7DD,England.

Parton et al. U.S. Pat. No. 4,459,347 discloses oxythioamido substitutedarylhydrazides to be useful in increasing the speed of negative workingsurface latent image silver halide emulsions and as nucleating agents indirect positive internal latent image forming silver halide emulsions.

Hess et al U.S. Ser. No. 493,480, filed May 11, 1983, commonly assigned,discloses sulfinic acid radical substituted arylhydrazides to beeffective for (i) increasing contrast of negative working surface latentimage forming silver halide emulsions, (ii) nucleating direct positiveinternal latent image forming silver halide emulsions, and (iii)increasing the speed of negative working emulsions of less than highcontrast when absorbed to grain surfaces. For applications (i) and (ii)ballasting groups are disclosed, such as alkyl, alkoxy, amido,carbamoyl, oxyamido, carbamoyloxy, carboxy, oxycarbamoyl, phenyl,alkylphenyl, phenoxy, and alkylphenoxy groups as well as groups whichare combinations thereof. For applications (ii) and (iii) the use anadsorption promoting moiety, such as an oxythioamido substituent, isdisclosed.

A patent literature summary of arylhydrazides employed to increasecontrast in negative working silver halide emulsions and to performnucleation in direct positive silver halide emulsions, which includes adiscussion of the mechanism of activity in each system is provided bythe following publication:

RD-3: Research Disclosure, Vol. 235, November 1983, Item 23510.

An oxycarbamido substituent of an arylhydrazide is disclosed.

SUMMARY OF THE INVENTION

In one aspect this invention is directed to an unballastedarylhydrazide, the aryl moiety of which is substituted with a group ofthe formula ##STR2## where one of X and X' represents --NH--, the otherrepresents a divalent chalcogen, and R represents an aliphatic oraromatic residue.

In another aspect this invention is directed to a high contrast negativeworking surface latent image forming silver halide emulsion comprised ofan unballasted arylhydrazide, the aryl moiety of which is substitutedwith a group according to formula (I).

In still another aspect this invention is directed to a negative workingphotographic element capable of producing halftone image comprised of asupport, an arylhydrazide, and a monodispersed surface latent imageforming silver halide emulsion capable of producing a high contrastimage in the presence of the arylhydrazide, further characterized inthat the arylhydrazide is an unballasted arylhydrazide, the aryl moietyof which is substituted with a group according to formula (I).

In an additional aspect this invention is directed to an improvedprocess for producing a halftone image by imagewise exposing through ahalftone mask a negative working photographic element comprised of asupport, an arylhydrazide, and a surface latent image forming silverhalide emulsion capable of producing a high contrast image in thepresence of the arylhydrazide, further characterized in that thearylhydrazide is an unballasted arylhydrazide, the aryl moiety of whichis substituted with a group according to formula (I).

It has been discovered that halftone images of good dot quality andacceptably low levels of pepper fog can be achieved when an unballastedarylhydrazide is employed containing an aryl sustituent satisfyingformula (I). Prior to this invention this desirable combination ofproperties has been achieved only by employing an arylhydrazide, thearyl moiety of which is substituted with a ureido group, in combinationwith a ballasted arylhydrazide. The requirement of a secondarylhydrazide and, particularly, a ballasted arylhydrazide adds to thecoating bulk of the photographic element. While a ureido substitutedarylhydazide when employed in combination with a ballastedarylhydrazide, can increase dot quality, the proportion of the ureidosubstituted arylhydrazide must be limited to avoid unacceptably highlevels of pepper fog. Thus, prior to the present invention the art hasbeen faced with the limitations of (i) employing a combination ofarylhydrazides and (ii) employing ureido substituted arylhydrazideswithin a narrow concentration range marked by poor dot quality on thelower border of the concentration range and unacceptably high pepper foglevels on the upper border of the concentration range. The presentinvention overcomes the limitations heretofore encountered in the art byallowing halftone images of good dot quality and acceptably low pepperfog levels to be achieved with a novel unballasted arylhydrazide thatcan be employed alone or, if desired, in combination with otherconventional arylhydrazides within a wide range of relative proportions.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better appreciated by reference to the followingdetailed description considered in conjunction with the drawings, inwhich FIG. 1 is a photograph enlarged 20X showing a typical pattern ofsevere pepper fog and

FIG. 2 is a photographic enlarged 20X showing the highest acceptablelevel of pepper fog.

DESCRIPTION OF PREFERRED EMBODIMENTS

The advantages realized with the present invention can be primarilyattributed to novel unballasted arylhydrazides, the aryl moiety of whichis substituted with a group satisfying formula (I), as described above.An unballasted arylhydrazide within the contemplation of the presentinvention can be represented by the following formula: ##STR3## whereinAc represents an activating group;

Ar represents a divalent aromatic group;

R represents an aliphatic or aromatic residue;

R¹ and R² can be either hydrogen or a sulfinic acid radical substituent,with the proviso that only one can be a sulfinic acid radicalsubstituent; and

one of X and X' represents --NH-- and the other represents a divalentchalcogen.

Although activating groups are not essential to increasing contrast withhydrazines, the most effective contrast increasing compounds arerecognized to include at least one activating group. A variety ofactivating groups are described in RD-3, cited above. Preferredactivating groups are acyl groups. Specifically preferred acyl groupscan be represented by the formula: ##STR4## where R³ is hydrogen or analiphatic or aromatic moiety. The highest activity levels are achievedwhen R³ is hydrogen. In another preferred form R³ can take the form ofan alkyl group, with lower alkyl groups of from 1 to 3 carbon atomsbeing preferred, since activity for corresponding aryl-hydrazidesgenerally declines as the number of carbon atoms forming the alkyl groupincreases. When R³ is an aromatic moiety, it is preferably a phenylgroup.

The divalent aromatic moiety Ar performs a stabilizing function byproviding a direct linkage of the β nitrogen atom of the hydrazide to atertiary carbon atom. In a preferred form the divalent aromatic moietyis a carbocyclic aromatic moiety--i.e., an arylene moiety, such asphenylene or naphthalene. In addition to the group represented byformula (I), the arylene moiety can be further ring substituted at anyremaining available position. Examples of other useful substituentsinclude hydroxy, amino, carboxy, alky, alkoxy, halo, and haloalkyl. Asherein defined cycloalkyl is subsumed within alkyl moieties. Unlessotherwise stated, all aliphatic and aromatic moieties referred to areunderstood to contain fewer than 8 carbon atoms. When Ar is a phenylenegroup, it can take the form of an o-, p-, or m-phenylene group, but itis most preferably a p-phenylene group with any additional substituents,if present, being preferably ortho substituents.

R can take the form of an aliphatic or aromatic residue. R should bechosen to retain mobility of the arylhydrazide in a silver halideemulsion or hydrophilic colloid layer of a photographic element. In oneform R can be an arylhydrazide. For example, it can take any of theforms of the arylhydrazide shown to the right of X' in formula (II). Ina preferred form R contains 8 or fewer carbon atoms. In a specificallypreferred form R is an alkyl group, optimally an alkyl group containingfrom 2 to 6 carbon atoms. In an aromatic form R is preferably phenyl.Five and six member heterocyclic ring containing aromatic residues arealso contemplated, such as pyridyl, thiazolyl, oxazolyl, and imidazolylgroups.

R^(1l) and R² are preferably hydrogen. It has been recognized that whenone of the nitrogen atoms of the hydrazino moiety is displaced by asulfinic acid radical substituent, preferably an arylsulfonyl group, anincrease in photographic speed can be realized. As between R¹ and R² itis preferred that R¹ be a sulfinic acid radical substituent. However,photographic speeds fully acceptable for halftone imaging applicationscan be readily achieved in the absence of a sulfinic acid radicalsubstituent attached to either of the nitrogen atoms α or β to the Acmoiety in formula (II), and overall characteristic curve shape in thetoe and shoulder regions is generally superior in the absence of thesulfinic acid radical subtituent.

When one of X and X' represents a divalent chalcogen (e.g., an oxy orthio linking atom), the other represents --NH--. When X is --NH--, X'can be chosen to complete a carbamoyloxy (--NH--C(O)--O--) orcarbamoylthio (--NH--C(O)--S--) group. In a specifically preferred formof the invention X' is represented by --NH--and X completes athiocarbamido (--S--C(O)--NH--) and, most preferably, an oxycarbamido(--O--C(O)--NH--) group.

From the foregoing it is apparent that specifically preferredarylhydrazides according to the present invention can be represented bythe following formula: ##STR5## where Ar is a phenylene, preferably ap-phenylene, group;

R is alkyl of from 1 to 8 carbon atoms, preferably 2 to 6 carbon atoms,or a phenyl substituent; and

R³ is hydrogen, lower alkyl of from 1 to 3 carbon atoms, or phenyl.

The following are illustrative of specific arylhydrazides within thecontemplation of this invention:

    ______________________________________                                        AH-1     2-(2,6-dichloro-4-methoxycarbamidophenyl)-                                    1-propionylhydrazine                                                 AH-2     2-(4-ethylcarbamoyloxyphenyl)-1-formyl-                                       hydrazine                                                            AH-3     2-(4-ethoxycarbamoylthiophenyl)-1-formyl-                                     hydrazine                                                            AH-4     2-(4-ethoxycarbamidophenyl)-1-formylhydrazine                        AH-5     2-(4-ethoxycarbamidophenyl)-1-formyl-2- -p-                                   tosylhydrazine                                                       AH-6     1-acetyl-2-(4-propoxycarbamidophenyl)hydra-                                   zine                                                                 AH-7     2-(4-butoxycarbamidophenyl)-1-formylhydrazine                        AH-8     2-(4-butylthiocarbamidophenyl)-1-formyl-                                      hydrazine                                                            AH-9     2-(4-butylcarbamoyloxyphenyl)-1-formyl-                                       hydrazine                                                            AH-10    1-benzoyl-2-(4-butylcarbamoylthio-2-tri-                                      fluoromethyl)hydrazine                                               AH-11    1-benzoyl-2-(2-pentoxycarbamidophenyl)-                                       hydrazine                                                            AH-12    2-(4-iso-propoxycarbamidophenyl)-1-formyl-                                    hydrazine                                                            AH-13    2-(4-hexoxycarbamidophenyl)-1-formylhydrazine                        AH-14    1-formyl-2-(4-phenoxycarbamidophenyl)-                                        hydrazine                                                            AH-15    1-formyl-2-(2-methoxy-4-N--pyridyloxycarb-                                    amidophenyl)hydrazine                                                AH-16    1-formyl-2-(2-N,N--diethylamine-4-phenyl-                                     thiocarbamidophenyl)hydrazine                                        ______________________________________                                    

The arylhydrazides of this invention can be incorporated in the silverhalide emulsion or other hydrophilic colloid layers of photographicelements in any effective concentration up to the limit of theirsolubility. Generally no advantage is realized from introducingconcentrations above about 10⁻² mole per mole of silver. Concentrationof levels of at least 10⁻³ mole per mole of silver are generallyemployed. A preferred concentration range for high halftone dot qualityis from above about 1.5×10⁻³ to 2×10⁻³ mole per mole of silver.

Athough not required, it is specifically recognized that thearylhydrazides of this invention can be employed in combination withconventional arylhydrazides, such as those disclosed in P-1 through P-6and RD-3, cited above and here incorporated by reference, known toincrease contrast in negative working surface latent image formingsilver halide emulsions. When one or more additional arylhydrazides areemployed, the total arylhydrazide concentration can still be maintainedwithin the ranges indicated above, but the minimum concentration of thenovel unballasted arylhydrazide can be reduced, with the preferredconcentration of the novel unballasted arylhydrazide being at least5×10⁻⁴ mole per mole of silver. Generally the molar ratio of the novelunballasted arylhydrazide to other arylhydazide should be at least 1 to2.

In one preferred form the arylhydrazides of this invention are employedin combination with conventional ballasted arylhydrazides. One or moreballasting moieties are preferably present in arylhydrazidesincorporated in photographic elements for the purpose of restrictingmobility of the arylhydrazides. Ballasted arylhydrazides, thoughrestricted in their mobility, are not confined to silver halide grainsurfaces and are to be distinguished from arylhydrazides having a silverhalide grain adsorption promoting moiety, such as a thiocarbonyl moiety.

Suitable ballasting groups can take conventional forms. For example, theballasting groups can be similar to those found in common incorporatedcouplers. Ballasting groups are generally recognized to require at least8 carbon atoms and frequently contain 30 or more carbon atoms. Theballast groups typically contain aliphatic and/or aromatic groups thatare relatively unreactive, such as alkyl, alkoxy, amido, carbamoyl,oxyamido, carbamoyloxy, carboxy, oxycarbonyl, phenyl, alkylphenyl,phenoxy, alkylphenoxy, and similar groups, with individual ballastsfrequently being comprised of combinations of these groups. Ballastedarylhydrazides, though restricted in mobility, retain sufficientresidual mobility to promote infectious development. Suitable ballastedarylhydrazides can be selected from among those disclosed by P-1 throughP-6 and RD-3.

The arylhydrazide compounds are employed in combination with negativeworking photographic emulsions comprised of radiation sensitive silverhalide grains capable of forming a surface latent image and a vehicle.The silver halide emulsions include the high chloride emulsionsconventionally employed in forming lith photographic elements as well assilver bromide and silver bromoiodide emulsions, which are recognized inthe art to be capable of attaining higher photographic speeds. Generallythe iodide content of the silver halide emulsions is less than about 10mole percent silver iodide, based on total silver halide.

The silver halide grains of the emulsions are capable of forming asurface latent image, as opposed to being of the internal latent imageforming type. Surface latent image silver halide grains are employed inthe overwhelming majority of negative working silver halide emulsions,whereas internal latent image forming silver halide grains, thoughcapable of forming a negative image when developed in an internaldeveloper, are usually employed with surface developers to form directpositive images. The distinction between surface latent image andinternal latent image silver halide grains is generally well recognizedin the art. Generally some additional ingredient or step is required inpreparation to form silver halide grains capable of preferentiallyforming an internal latent image as compared to a surface latent image.

Although the difference between a negative image produced by a surfacelatent image emulsion and a positive image produced by an internallatent image emulsion when processed in a surface developer is aqualitative difference which is visually apparent to even the unskilledobserver, a number of tests have been devised to distinguishquantitatively surface latent image forming and internal latent imageforming emulsions. For example, according to one such test when thesensitivity resulting from surface development (A), described below, isgreater than that resulting from internal development (B), describedbelow, the emulsion being previously light exposed for a period of from1 to 0.01 second, the emulsion is of a type which is "capable of forminga surface latent image" or, more succinctly, it is a surface latentimage emulsion. The sensitivity is defined by the following equation:

    S=100/Eh

in which S represents the sensitivity and Eh represents the quantity ofexposure necessary to obtain a mean density--i.e., 1/2 (D-max+D-min).

Surface Development (A)

The emulsion is processed at 20° C. for 10 minutes in a developersolution of the following composition:

    ______________________________________                                        N--methyl- -p-aminophenyl hemisulfate                                                                  2.5   g                                              Ascorbic acid            10    g                                              Sodium metaborate (with 4                                                                              35    g                                              molecules of water)                                                           Potassium bromide        1     g                                              Water to bring the total to                                                                            1     liter.                                         ______________________________________                                    

Internal Development (B)

The emulsion is processed at about 20° C. for 10 minutes in a bleachingsolution containing 3 g of potassium ferricyanide per liter and 0.0125 gof phenosafranine per liter and washed with water for 10 minutes anddeveloped at 20° C. for 10 minutes in a developer solution having thefollowing composition:

    ______________________________________                                        N--methyl- -p-aminophenol hemisulfate                                                                  2.5   g                                              Ascorbic acid            10    g                                              Sodium metaborate (with 4                                                                              35    g                                              moles of water)                                                               Potassium bromide        1     g                                              Sodium thiosulfate       3     g                                              Water to bring the total to                                                                            1     liter.                                         ______________________________________                                    

The silver halide grains, when the emulsions are used for lithapplications, have a mean grain size of not larger than about 0.7micron, preferably about 0.4 micron or less. Mean grain size is wellunderstood by those skilled in the art, as illustrated by Mees andJames, The Theory of the Photographic Process, 3rd Ed., MacMillan 1966,Chapter 1, pages 36-43. The photographic emulsions of this invention arecapable of producing higher photographic speeds than would be expectedfrom their mean grain sizes. The photographic emulsions can be coated toprovide emulsion layers in the photographic elements of any conventionalsilver coverage. Common conventional silver coating coverages fallwithin the range of from about 0.5 to about 10 grams per square meter.

As is generally recognized in the art, higher contrasts can be achievedby employing relatively monodispersed emulsions, particularly whenlarger grain size emulsions are employed. As herein employed, the term"monodispersed" is employed to indicate emulsions having a coefficientof variation of less than 20%. For the highest levels of contrast it isgenerally preferred that the monodispersed emulsions have a coefficientof variation of less than 10%. (As employed herein the coefficient ofvariation is defined as 100 times the standard deviation of the graindiameter divided by the average grain diameter.)

Silver halide emulsions contain in addition to silver halide grains avehicle. The proportion of vehicle can be widely varied, but typicallyis within the range of from about 20 to 250 grams per mole of silverhalide. Excessive vehicle can have the effect of reducing maximumdensity and consequently also reducing contrast. Thus for contrastvalues of 10 or more it is preferred that the vehicle be present in aconcentration of 250 grams per mole of silver halide or less. Thespecific vehicle materials present in the emulsion and any other layersof the photographic elements can be chosen from among conventionalvehicle materials. Preferred vehicles are water permeable hydrophiliccolloids employed alone or in combination with extenders such assynthetic polymeric peptizers, carriers, latices, and binders. Suchmaterials are more specifically described in Research Disclosure, Vol.176, December 1978, Item 17643, Section IX. Vehicles are commonlyemployed with one or more hardeners, such as those described in SectionX.

Emulsions according to this invention having silver halide grains of anyconventional geometric form (e.g., regular octahedral or, preferably,cubic crystalline form) can be prepared by a variety oftechniques--e.g., single-jet, double-jet (including continuous removaltechniques), accelerated flow rate and interrupted precipitationtechniques, as illustrated by Trivelli and Smith, The PhotographicJournal, Vol. LXXIX, May, 1939pages 330--338; T. H. James The Theory ofthe Photographic Process, 4th Ed., Macmillan, 1977, Chapter 3;Terwilliger et al Research Disclosure, Vol. 149, September 1976, Item14987; Research Disclosure, Vol. 225, January 1983, Item 22534; as wellas Nietz et al U.S. Pat. No. 2,222,264; Wilgus German OLS 2,107,118;Lewis U.K. Pat. Nos. 1,335,925, 1,430,465 and 1,469,480; Irie et al U.S.Pat. No. 3,650,757; Morgan U.S. Pat. No. 3,917,485 (where pAg cycling islimited to permit surface development); and Miusliner U.S. Pat. No.3,790,287. Double-jet accelerated flow rate precipitation techniques arepreferred for forming monodispersed emulsions. Sensitizing compounds,such as compounds of copper, thallium, cadmium, rhodium, tungsten,thorium, iridium and mixtures thereof, can be present duringprecipitation of the silver halide emulsion, as illustrated by Arnold etal U.S. Pat. No. 1,195,432; Hochstetter U.S. Pat. No. 1,951,933;Trivelli et al, U.S. Pat. No. 2,448,060; Overman U.S. Pat. No.2,628,167; Mueller U.S. Pat. No. 2,950,972; Sidebotham U.S. Pat. No.3,488,709; and Rosecrants et al U.S. Pat. No. 3,737,313.

The individual reactants can be added to the reaction vessel throughsurface or sub-surface delivery tubes by gravity feed or by deliveryapparatus for maintaining control of the pH and/or pAg of the reactionvessel contents, as illustrated by Culhane et al U.S. Pat. No.3,821,002, Oliver U.S. Pat. No. 3,031,304 and Claes et alPhotographische Korrespondenz, Band 102, Number 10, 1967, page 162. Inorder to obtain rapid distribution of the reactants within the reactionvessel, specially constructed mixing devices can be employed, asillustrated by Audran U.S. Pat. No. 2,996,287, McCrossen et al U.S. Pat.No. 3,342,605, Frame et al U.S. Pat. No. 3,415,650, Porter et al U.S.Pat. No. 3,785,777, Saito et al German OLS 2,556,885 and Sato et alGerman OLS 2,555,365. An enclosed reaction vessel can be employed toreceive and mix reactants upstream of the main reaction vessel, asillustrated by Forster et al U.S. Pat. No. 3,897,935 and Posse et alU.S. Pat. No. 3,790,386.

The grain size distribution of the silver halide emulsions can becontrolled by silver halide grain separation techniques or by blendingsilver halide emulsions of differing grain sizes. The emulsions caninclude ammoniacal emulsions, as illustrated by Glafkides, PhotographicChemistry, Vol. 1, Fountain Press, London, 1958, pages 365-368 and pages301-304; thiocyanate ripened emulsions, as illustrated by IllingsworthU.S. Pat. No. 3,320,069; thioether ripened emulsions as illustrated byMcBride U.S. Pat. No. 3,271,157, Jones U.S. Pat. No. 3,574,628 andRosecrants et al U.S. Pat. No. 3,737,313 or emulsions containing weaksilver halide solvents, such as ammonium salts, as illustrated byPerignon U.S. Pat. No. 3,784,381 and Research Disclosure, Vol. 134, June1975, Item 13452.

The silver halide emulsion can be unwashed or washed to remove solublesalts. The soluble salts can be removed by chill setting and leaching,as illustrated by Craft U.S. Pat. No. 2,316,845 and McFall et al U.S.Pat. No. 3,396,027; by coagulation washing, as illustrated by Hewitsonet al U.S. Pat. No. 2,618,556, Yutzy et al U.S. Pat. No. 2,614,928.Yackel U.S. Pat. No. 2,565,418, Hart et al U.S. Pat. No. 3,241,969,Waller et al U.S. Pat. No. 2,489,341, Klinger U.K. Patent 1,305,409 andDersch et al U.K. Patent 1,167,159; by centrifugation and decantation ofa coagulated emulsion, as illustrated by Murray U.S. Pat. No. 2,463,794,Ujihara et al U.S. Pat. No. 3,707,378, Audran U.S. Pat. No. 2,996,287and Timson U.S. Pat. No. 3,498,454; by employing hydrocyclones alone orin combination with centrifuges, as illustrated by U.K. Patent1,336,692, Claes U.K. Patent 1,356,573 and Ushomirskii et al SovietChemical Industry, Vol. 6No. 3, 1974, pages 181-185; by diafiltrationwith a semipermeable membrane, as illustrated by Research Disclosure,Vol. 102, October 1972, Item 10208, Hagemaier et al Research Disclosure,Vol. 131, March 1975, Item 13122, Bonnet Research Disclosure, Vol.135July 1975, Item 13577, Berg et al German OLS 2,436,461 and BoltonU.S. Pat. No. 2,495,918 or by employing an ion exchange resin, asillustrated by Maley U.S. Pat. No. 3,782,953 and Noble U.S. Pat. No.2,827,428. The emulsions, with or without sensitizers, can be dried andstored prior to use as illustrated by Research Disclosure, Vol. 101,September 1972, Item 10152.

For high contrast photographic applications high levels of photographicspeed are not necessarily required. Thus, the emulsions employed neednot be chemically sensitized. Sensitization with one or more middlechalcogens, sulfur, selenium, and/or tellurium, is a preferred surfacechemical sensitization. Such sensitization can be achieved by the use ofactive gelatin or by the addition of middle chalcogen sensitizers, suchas disclosed by Research Disclosure, Item 17643, cited above, SectionIII. Reduction and other conventional chemical sensitization techniquesdisclosed therein which do not unacceptably reduce contrast can also beemployed.

Spectral sensitization of the high contrast silver halide emulsions isnot required, but can be undertaken conventional spectral sensitizers,singly or in combination, as illustrated by Research Disclosure, Item17643, cited above Section IV. For black-and-white imagingorthochromatic and panchromatic sensitizations are frequently preferred.

By suitable choice of substituent groups the dyes can be cationic,anionic or nonionic. Preferred dyes are cationic cyanine and merocyaninedyes. Emulsions containing cyanine and merocyanine dyes have beenobserved to exhibit relatively high contrasts. Spectral sensitizing dyesspecifically preferred for use in the practice of this invention are asfollows:

    ______________________________________                                        SS-1     Anhydro-5,5'-dichloro-9-ethyl-3,3'-bis-(3-                                    sulfopropyl)oxacarbocyanine hydroxide,                                        sodium salt                                                          SS-2     5,5',6,6'-Tetrachloro-1,1',3,3'-tetra-                                        ethylbenzimidazolocarbocyanine iodide                                SS-3     3,3'-Diethyl-9-methylthiacarbocyanine                                         bromide                                                              SS-4     3,3-Diethyloxacarbocyanine iodide                                    SS-5     5,5'-Dichloro-3,3',9-triethylthiacarbo-                                       cyanine bromide                                                      SS-6     3,3'-Diethylthiocarbocyanine iodide                                  SS-7     5,5'-Dichloro-2,2'-diethylthiocarbocyanine,                                    -p-toluene sulfonate salt                                           SS-8     3-Carboxymethyl-5-[(3-methyl-2-thia-                                          zolidinylidene)-2-methylethylidene]rhodanine                         SS-9     3-Ethyl-3-[(3-ethyl-2-thiazolidinylidene)-                                    2-methylethylidene]rhodanine                                         SS-10    5-[(3-{2-Carboxyethyl}-2-thia-                                                zolidinylidene)ethylidene]-3-ethylrhodanine                          SS-11    1-Carboxymethyl-5-[(3-ethyl-2-benzothia-                                      zolinylidene)ethylidene]-3-phenyl-2-thio-                                     hydantoin                                                            SS-12    1-Carboxymethyl-5-[(1-ethyl-2(H)--naphtho-                                    {1,2-d}thiazolin-2-ylidene)ethyli-                                            dene]-3-phenyl-2-thiohydantoin                                       SS-13    3-Carboxymethyl-5-[(3-ethyl-2-benzothia-                                      zolinylidene)ethylidene]rhodanine                                    SS-14    5-[(3-Ethyl-2-benzoxazolinylidene)ethyl-                                      idene]-3-heptyl-2-thio-2,4-oxazolidinedione                          SS-15    3-Carboxymethyl-5-(3-ethyl-2-benzothia-                                       zolinylidene)rhodanine                                               SS-16    3-Carboxymethyl-5-(3-methyl-2-benzoxa-                                        zolinylidene)rhodanine                                               SS-17    3-Ethyl-5-[(3-ethyl-2-benzoxazolinyli-                                        dene)ethylidene]rhodanine                                            ______________________________________                                    

The photographic elements can be protected against fog by incorporationof antifoggants and stabilizers in the element itself or in thedeveloper in which the element is to be processed. Conventionalantifoggants, such as those disclosed by Mifune et al U.S. Pat. Nos.4,241,164, 4,311,781, 4,166,742, and 4,237,214, and Okutsu et al U.S.Pat. No. 4,221,857, can be employed.

Preferred antifoggants are benzotriazoles, such as benzotriazole (thatis, the unsubstituted benzotriazole compound), halo-substitutedbenzotriazoles (e.g., 5-chlorobenzotriazole, 4-bromobenzotriazole, and4-chlorobenzotriazole), and alkyl-substituted benzotriazoles wherein thealkyl moiety contains from about 1 to 12 carbon atoms (e.g.,5-methylbenzotriazole).Other known useful antifoggants includebenzimidazoles, such as 5-nitrobenzimidazoles; benzothiazoles, such as5-nitrobenzothiazole and 5-methylbenzothiazole; heterocyclic thiones,such as, 1-methyl-2-tetrazoline-5-thione; triazines, such as2,4-dimethylamino-6-chloro-5-triazine; benzoxazoles, such asethylbenzoxazole; and pyrroles, such as 2,5-dimethylpyrrole.

The antifoggants can be employed in conventional concentrations. Thebenzotriazole can be located in the emulsion layer or in any hydrophiliccolloid layer of the photographic element in a concentration in therange of from 10⁻⁴ to 10⁻¹, preferably 10⁻³ to 3×10⁻², mole per mole ofsilver. When the benzotriazole antifoggant is added to the developer, itis employed in a concentration of from 10⁻⁶ to about 10⁻¹, preferably 3×10⁻⁵ and 3 ×10⁻², mole per liter of developer.

In addition to the components of the photographic emulsions and otherhydrophilic colloid layers described above it is appreciated that otherconventional element addenda compatible with obtaining relatively highcontrast silver images can be present. For example, the photographicelements can contain developing agents (described below in connectionwith the processing steps), development modifiers, plasticizers andlubricants, coating aids, antistatic material, and matting agents, theseconventional materials being illustrated in Research Disclosure, citedabove, Item 17643, Sections XII, XIII, XVI, and XX. The elements can beexposed as described in Section XVIII.

The light sensitive silver halide contained in the photographic elementscan be processed following exposure to form a relatively high contrastimage by associating the silver halide with an aqueous alkaline mediumin the presence of a developing agent contained in the medium or theelement. Processing formulations and techniques are described in L. F.Mason, Photographic Processing Chemistry, Focal Press, London, 1966;Processing Chemicals and Formulas, Publication J-1, Eastman KodakCompany, 1973; Photo-Lab Index, Morgan and Morgan, Inc., Dobbs Ferry,New York 1977; and Neblette's Handbook of Photographic and ReprographicMaterials, Processes and Systems, VanNostrand Reinhold Company, 7th Ed.,1977.

It is a distinct advantage of the present invention that thephotographic elements can be processed in conventional developersgenerally as opposed to specialized developers conventionally employedin conjunction with lith photographic elements to obtain very highcontrast images. When the photographic elements contain incorporateddeveloping agents, the elements can be processed in an activator, whichcan be identical to the developer in composition, but lacking adeveloping agent. Very high contrast images can be obtained at pH valuesin the range of from 10 to 13.0, preferably 10.5 to 12.5. It is also anadvantage of this invention that relatively high contrast images can beobtained with higher concentrations of preservatives to reduce aerialoxidation of the developing agents, such as alkali sulfites (e.g.,sodium or potassium sulfite, bisulfite or metasulfite) than hasheretofore been feasible in traditional lith processing. This allows thedevelopers to be stored for longer periods. Any preservative orpreservative concentration conventional in lower contrast processing canbe employed, such as, for instance, a sulfite ion concentration in therange of from about 0.15 to 1.2 mole per liter of developer.

The developers are typically aqueous solutions, although organicsolvents, such as diethylene glycol, can also be included to facilitatethe solvency of organic components. The developers contain one or acombination of conventional developing agents, such aspolyhydroxybenzene, aminophenol, para-phenylenediamine, ascorbic acid,pyrazolidone, pyrazolone, pyrimidine, dithionite, hydroxylamine or otherconventional developing agents. It is preferred to employ hydroquinoneand 3-pyrazolidone developing agents in combination. The pH of thedevelopers can be adjusted with alkali metal hydroxides and carbonates,borax and other basic salts. To reduce gelatin swelling duringdevelopment, compounds such as sodium sulfate can be incorporated intothe developer. Also, compounds such as sodium thiocyanate can be presentto reduce granularity. Also, chelating and sequestering agents, such asethylenediaminetetraacetic acid or its sodium salt, can be present.Generally, any conventional developer composition can be employed in thepractice of this invention. Specific illustrative photographicdevelopers are disclosed in the Handbook of Chemistry and Physics, 36thEdition, under the title "Photographic Formulae" at page 3001 et seq.,and in Processing Chemicals and Formulas, 6th Edition, published byEastman Kodak Company (1963), the disclosures of which are hereincorporated by reference. The photographic elements can, of course, beprocessed with conventional developers for lith photographic elements,as illustrated by Masseth U.S. Pat. No. 3,573,914 and VanReusel U.K.Patent 1,376,600. A preferred developer is disclosed by P-7.

Examples

The invention can be better appreciated by reference to the followingspecific examples:

Comparative Coatings 1 through 12

Comparative Coatings 1 through 12 illustrate the poor level of pepperfog obtained when non-carbamate nucleating agents are used in ahigh-contrast lith film alone or in combination. The nucleating agentsare 1-formyl-2-{4-[2-(2,4-di-t-pentylphenoxy)butyramido]phenyl}hydrazine(N-1) and 1-[4-(2-formylhydrazino)phenyl]-3-n-hexyl-urea (N-2).

On a polyester support was coated a layer comprising a monodispersed0.22 μm AgBrI (2.5 mole % iodide) emulsion at 3.50 g/m² Ag, 2.47 g/m²gelatin, and 1.06 g/m² of a latex copolymer of methyl acrylate,2-methyl-2-acrylamido-1-propanesulfonic acid, and acetoacetoxyethylmethacrylate (90:4:6 monomer weight ratio). No chemical sensitizationstep was performed on the emulsion. The emulsion was spectrallysensitized with 216 mg/Ag mole ofanhydro-5,5'-dichloro-9-ethyl-3,3'-di-(3-sulfopropyl)oxacarbocyaninehydroxide, triethylamine salt. Additions of nucleating agents N-1 andN-2 were made as listed in Table I, totaling 11×10⁻⁴ moles/Ag mole. Aprotective overcoat of 1.38 g/m² gelatin was coated over the emulsionlayer.

Samples of the coatings were exposed through a step tablet for 1 sec toa 600-watt 3000° K. quartz halogen source in an Eastman Model 1BSensitometer and processed in a KODALITH Model 324® processor, withdevelopment in a developer of the type disclosed in U.S. Pat. No.4,269,929 for 85 sec at 29.5° C. The speed, γ, and qualitatively rateddot quality and pepper fog levels are tabulated in Table I. The relativespeeds are normalized to that of Coating 1 taken as 100.

The results of Table I show that combinations of nucleating agents N-1and N-2 provided acceptable halftone image and pepper fog propertiesonly in a single coating.

                  TABLE I                                                         ______________________________________                                        Moles ×                                                                              Nucleators N-1 and N-2                                           Coating                                                                              10.sup.4  Relative      Dot    Pepper                                  No.    N-1    N-2    Speed  γ                                                                            Quality                                                                              Fog                                   ______________________________________                                        C-1    11     0      100    9.5  Soft Dots                                                                            None                                  C-2    10     1      162    15.8 Soft Dots                                                                            None                                  C-3    9      2      276    23.3 Marginal                                                                             None                                  C-4    8      3      302    24.2 Good   Acceptable                            C-5    7      4      309    24.3 Good   Unacceptable                          C-6    6      5      339    29.4 Good   Unacceptable                          C-7    5      6      389    30.1 Good   Unacceptable                          C-8    4      7      389    30.8 Good   Unacceptable                          C-9    3      8      363    35.8 Good   Unacceptable                           C-10  2      9      347    33.1 Good   Unacceptable                           C-11  1      10     363    31.3 Good   Unacceptable                           C-12  0      11     380    38.0 Good   Severe                                ______________________________________                                    

Comparative Coatings 13 through 32

These coatings show that excellent half-tone dot quality with completeabsence of pepper fog can be obtained by use of the combination ofnucleating agent N-1 and a nucleating agent of the invention,2-(4-n-butoxycarbamidophenyl)-1-formylhydrazine (AH-7).

The coatings were prepared, exposed, and processed as described above,but with nucleating agent additions as listed in Table II. A totalnucleating agent level of 19×10⁻⁴ moles per Ag mole was used in eachcoating. The results are tabulated in Table II. The relative speeds arenormalized to that of Coating 1 of Table I taken as 100.

The results of Table II show that the combination of nucleating agentsN-1 and AH-7 provided acceptable halftone image quality and pepper fogproperties over a wide range of relative proportions. When nucleatingagent AH-7 of the invention was used alone (Coating No. 32), excellentdot quality was obtained with only a slight level of pepper fog.

                  TABLE II                                                        ______________________________________                                                    Nucleating Agents N-1 and AH-7                                    Coating                                                                              Moles × 10.sup.4                                                                   Relative      Dot     Pepper                                No.    N-1    AH-7    Speed  γ                                                                            Quality Fog                                 ______________________________________                                        13     19      0       89    10.4 Soft Dots                                                                             None                                14     18      1      138    12.9 Soft Dots                                                                             None                                15     17      2      214    13.8 Soft Dots                                                                             None                                16     16      3      246    16.1 Marginally                                                                            None                                                                  Acceptable                                  17     15      4      234    18.3 Marginally                                                                            None                                                                  Acceptable                                  18     14      5      240    20.4 Good    None                                19     13      6      276    19.2 Good    None                                20     12      7      276    23.7 Excellent                                                                             None                                21     11      8      276    24.9 Excellent                                                                             None                                22     10      9      295    23.1 Excellent                                                                             None                                23      9     10      276    20.7 Excellent                                                                             None                                24      8     11      269    23.2 Excellent                                                                             None                                25      7     12      295    25.2 Excellent                                                                             None                                26      6     13      302    24.8 Excellent                                                                             None                                27      5     14      289    24.3 Excellent                                                                             None                                28      4     15      302    25.5 Excellent                                                                             None                                29      3     16      295    24.3 Excellent                                                                             None                                30      2     17      309    26.1 Excellent                                                                             Very                                                                          Slight                              31      1     18      309    25.6 Excellent                                                                             Very                                                                          Slight                              32      0     19      316    22.7 Excellent                                                                             Slight                              ______________________________________                                    

Comparative Coatings 33 through 46

Comparative Example 3 shows that nucleating agent N-2 when used alone isunable to provide both good half-tone dot quality and an acceptablepepper fog level, while nucleating agent AH-7 of the invention usedalone can provide excellent dot quality at an acceptable pepper foglevel.

The coatings were prepared, exposed and processed as described above,but with the nucleating agent additions as listed in Table III. Theresults are tabulated in Table III, with the relative speeds normalizedto that of Coating 1 of Table I taken as 100.

The results of Table III show that as the level of nucleating agent N-2was increased, half-tone dot quality increased, but the pepper fograpidly reached an unacceptable level. In the case of nucleating agentAH-7 of the invention, however, the pepper fog remained at a fullyacceptable level while an excellent dot quality was achieved.

                  TABLE III                                                       ______________________________________                                                    Nucleating Agents N-2 and AH-7                                                      Rela-                                                       Coating                                                                              Moles × 10.sup.4                                                                   tive         Dot    Pepper                                  No.    N-2    AH-7    Speed γ                                                                            Quality                                                                              Fog                                   ______________________________________                                        33     1       0      110   6.1  Soft Dot                                                                             Acceptable                            34     2       0      214   12.7 Soft Dots                                                                            Acceptable                            35     3       0      257   27.3 Marginal                                                                             Acceptable                            36     4       0      295   15.6 Good   Unacceptable                          37     5       0      309   19.5 Good   Unacceptable                          48     6       0      331   27.6 Good   Unacceptable                          39     0      12      240   16.4 Marginal                                                                             Acceptable*                           40     0      13      246   16.5 Marginal                                                                             Acceptable*                           41     0      14      257   18.1 Good   Acceptable*                           42     0      15      257   17.4 Good   Acceptable*                           43     0      16      269   19.3 Excellent                                                                            Acceptable*                           44     0      17      282   17.4 Excellent                                                                            Acceptable*                           45     0      18      282   20.3 Excellent                                                                            Acceptable*                           46     0      19      389   18.2 Excellent                                                                            Acceptable*                           ______________________________________                                    

Investigations of 2-(4-hexoxycarbamidophenyl)-1-formylhydrazine (AH-13)and 1-formyl-2-(4-phenoxycarbamidophenyl)hydrazine (AH-14) alsodemonstrated satisfactory performance levels, whether employed alone orin combination with N-1.

Preparations of the novel unballasted arylhydrazides of this inventioncan be readily appreciated from the following illustrative preparation:

Preparation of 2-(4-ethylcarbamoyloxyphenyl)-1-formylhyrazine (AH-2)

Ethylchloroformate (9.01 g., 0.066 mol) was added dropwise to asuspension of 4-amino-1-(2'-formylhydrazino)benzene (10.0 g., 0.066 mol)and 2,6-lutidine (7.1 g, 0.066 mol) in acetonitrile (250 ml). Uponheating to reflux, the reaction mixture became homogenous. After threehours the reaction had gone to completion as evidenced by thin layerchromatographic examination. The solvent was removed under reducedpressure. The resulting solid was slurried in water and filtered toremove any water soluble amine starting material. The collected solidwas slurried in diethyl ether and filtered to remove ether solubleimpurities. The collected solid was recrytallized from methanol to yielda white solid (11.4 g., 77% of theoretical yield, melting point 134°C.).

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention.

What is claimed is:
 1. An unballasted arylhydrazide, the aryl moiety ofwhich is substituted with a group of the formula ##STR6## where one of Xand X' represents -NH-, the other represents a divalent chalcogen, and Rrepresents an aliphatic or aromatic residue.
 2. An unballastedarylhydrazide according to claim 1 wherein R contains 8 or fewer carbonatoms.
 3. An unballasted arylhydrazide according to claim 1 wherein X'is -NH-.
 4. An unballasted arylhydrazide according to claim 1 wherein Xis -O- or -S-.
 5. An unballasted arylhydrazide according to claim 1wherein R contains 2 to 6 carbon atoms, X is -O-, and X' is -NH-.